In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure of radial rays such as light or electron beam through a mask having a predetermined pattern, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film.
A resist material in which the exposed portions become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of pattern miniaturization. Typically, these miniaturization techniques involve shortening the wavelength (increasing the energy) of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in mass production. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a wavelength shorter (energy higher) than these excimer lasers, such as electron beam (EB), extreme ultraviolet radiation (EUV), and X ray.
As shortening the wavelength of the exposure light source progresses, it is required to improve various lithography properties of the resist material, such as the sensitivity to the exposure light source and a resolution capable of reproducing patterns of minute dimensions. As resist materials which satisfy such requirements, chemically amplified resists are known. As a chemically amplified composition, a composition including a base material component that exhibits a changed solubility in an alkali developing solution under the action of acid and an acid-generator component that generates acid upon exposure is generally used. For example, in a chemically amplified positive resist composition, a base component which exhibits increased solubility in an alkali developing solution under action of acid is used.
Conventionally, a resin (base resin) is typically used as the base component of a chemically amplified resist composition. In the case of a positive type, a resin that exhibits increased solubility in an alkali developing solution under action of acid is used as a base resin.
Resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are used as base resins for chemically amplified resist compositions that use ArF excimer laser lithography, as they exhibit excellent transparency in the vicinity of 193 nm (for example, see Patent Document 1). Here, the term “(meth)acrylic acid” is a generic term that includes either or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position. The term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position. The term “(meth)acrylate” is a generic term that includes either or both of the acrylate having a hydrogen atom bonded to the α-position and the methacrylate having a methyl group bonded to the α-position.
Furthermore, currently, in addition to the base resin and the acid generator, a nitrogen-containing organic compound such as an alkylamine, an alkylalcoholamine or the like is added to chemically amplified resists (see, for example, Patent Documents 2 and 3). The nitrogen-containing organic compound functions as a quencher which traps the acid generated from the acid generator, and contributes to improving various lithography properties such as the shape of the resist pattern.